The Meteorology, Climatology, and Geophysics Agency (Badan Meteorologi, Klimatologi, dan Geofisika, or BMKG) predicts a delayed start to Indonesia’s 2026/2027 rainy season, with most regions expected to enter the rainy season between November and December 2026.
According to the BMKG, the onset of Indonesia’s 2026/2027 rainy season will be delayed due to the influence of a very strong El Niño and a positive Indian Ocean Dipole (IOD). Both climate phenomena have the potential to reduce rainfall in several regions. Consequently, most parts of Indonesia are expected to enter the rainy season between November and December 2026. Meanwhile, the rainy season is predicted to peak between December 2026 and February 2027.
“The nature of the rainfall will be normal—meaning the total precipitation will be in line with the climatological average of the last 30 years—but it will occur over a shorter period. Consequently, we can expect heavy, very heavy, and even extreme rainfall to occur more frequently from the end of this year through the beginning of next year,” the Head of BMKG, Teuku Faisal Fathani, said at the State Palace on Wednesday, the 21st of October.
More specifically, the BMKG estimates that the rainy season will begin later than usual in 529 seasonal zones, covering 61.08% of Indonesia’s land area. Meanwhile, 26 seasonal zones, accounting for 2.15% of the country’s land area, are expected to enter the rainy season at the usual time.
Regarding rainfall, cumulative precipitation throughout the rainy season in 510 seasonal zones, covering 69.76% of Indonesia’s land area, is projected to fall within the normal category, meaning it will be close to the climatological average.
Based on the BMKG’s forecast for the onset of the 2026/2027 rainy season, the following regions are expected to enter the rainy season in November 2026:
- Parts of Sumatra;
- Parts of Java;
- Parts of Kalimantan;
- Parts of Bali;
- Parts of West Nusa Tenggara;
- A small portion of East Nusa Tenggara;
- Parts of Sulawesi;
- Parts of North Maluku;
- Parts of Maluku;
- The northern part of West Papua; and
- Parts of South Papua.
Meanwhile, the following regions are expected to enter the rainy season in December 2026:
- Parts of Lampung;
- Most of Java;
- Parts of South Kalimantan;
- Most of Bali;
- Most of West Nusa Tenggara;
- Most of East Nusa Tenggara;
- Most of Sulawesi;
- Parts of North Maluku;
- Parts of Maluku; and
- The southern part of South Papua.